The present invention relates to a wiring board having a circuit component connected to an insulating film on which a wire pattern is formed and capable of being mounted in a bent condition in an electric device.
In an inkjet printer, color printing is performed using a plurality of ink cartridges, such as cyan, magenta, yellow and black ink cartridges. Inks supplied from a plurality of ink cartridges are ejected from a plurality of ejection outlets formed in an inkjet head by pressure generated by a piezoelectric element. The piezoelectric element generates pressure according to a drive voltage supplied from a driving IC, and the drive voltage from the driving IC is supplied to the piezoelectric element through a flexible wiring board.
The flexible wiring board is a flexible board with a plurality of wires provided on one surface or both surfaces of an insulating film. Using the flexible wiring board for the transmission of a drive voltage, a control signal, etc. is advantageous because it is possible to increase the degree of freedom in mounting an inkjet head in an inkjet printer and it is possible to decrease the size of the inkjet printer. In recent years, a COF (Chip On Film) having a driving IC connected directly to a flexible wiring board has been put into practical use. Since the COF can shorten the distance from the driving IC to the piezoelectric element, it is possible to reduce the attenuation and delay of the drive voltage, and it is possible to efficiently drive the piezoelectric element.
Moreover, since the COF can be mounted in a bent condition in the inkjet printer, it has advantages that it is possible to decrease the size of the inkjet printer and increase the degree of freedom in designing the inkjet printer. However, since the driving IC is connected to the wire on the insulating film of the COF by solder, if the insulating film is bent, bending stress is applied to the connection section connected by the solder, and there is a possibility that the connection between the insulating film and the driving IC maybe destroyed.
In the case where a liquid crystal driving IC is mounted on a flexible board on which a plurality of wires are provided, Japanese Patent Application Laid-Open No. 2003-273486 proposed a mount structure that improved the bending resistance of the flexible board by making wires placed on both sides of the liquid crystal driving IC among the plurality of wires wider than the other wires. In Japanese Patent Application Laid-Open No. 2003-273476, wide dummy wires are further provided outside the both wide wires to further improve the bending resistance.